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43rd AIAA Aerospace Sciences Meeting and Exhibit

作者： Yuan, X. Caraballo, E. Yan, P. Özbay, H. Serrani, A. DeBonis, J. Myatt, J.H. Samimy, M. Collaborative Center of Control Science Ohio State University United States Department of Electrical and Computer Engineering Department of Mechanical Engineering United States Bilkent Univ. Dept. of Electrical and Electronics Eng. Ankara Turkey NASA Glenn's Quiet Aircraft Technology Program United States Air Force Research Laboratory Air Vehicles Directorate WPAFB United States

This paper explores feedback controller design for cavity flows based on reduced-order models derived using Proper Orthogonal Decomposition (POD) along with Galerkin projection method. Our preliminary analysis shows that the equilibrium of the POD model is unstable and a static output feedback controller cannot stabilize it. We develop Linear Quadratic (LQ) optimal state feedback controllers and LQ optimal observers for the linearized models. The linear controllers and observers are applied to the nonlinear system using simulations. The controller robustness is numerically tested with respect to different POD models generated at different forcing frequencies. An estimation for the region of attraction of the linear controllers is also provided.

关键词： Subsonic flow

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A comparative evaluation of competitive learning algorithms for edge detection enhancement

A comparative evaluation of competitive learning algorithms ...

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European Signal Processing Conference (EUSIPCO)

作者： Tuba Sirin Mehmet Izzet Saglam Isin Erer Muhittin Gokmen Okan Ersoy Informatics Institute Computer Science and Engineering Informatics Institute Satellite Communication and Remote Sensing Program Faculty of Electrical and Electronic Engineering Electronics and Communication Department Faculty of Electrical and Electronic Engineering Istanbul Technical University Maslak Istanbul TURKEY Purdue University School of Electrical and Computer Engineering West Lafayette Indiana USA

Most edge detection algorithms include three main stages: smoothing, differentiation, and labeling. In this paper, we evaluate the performance of algorithms in which competitive learning is applied first to enhance edges, followed by an edge detector to locate the edges. In this way, more detailed and relatively more unbroken edges can be found as compared to the results when an edge detector is applied alone. The algorithms compared are K-Means, SOM and SOGR for clustering, and Canny and GED for edge detection. Perceptionally, best results were obtained with the GED-SOGR algorithm. The SOGR is also considerably simpler and faster than the SOM algorithm.

关键词： Image edge detection Image segmentation Vectors Abstracts Filtering algorithms Erbium Training

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High-power packages for phosphor-based white-light-emitting diode lamps

High-power packages for phosphor-based white-light-emitting ...

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2005 International Semiconductor Device Research Symposium

作者： Luo, Hong Kim, Jong Kyu Xi, Yangang Cho, Jaehee Sone, Cheolsoo Park, Yongjo Schubert, E. Fred Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute Troy NY 12180 Electrical Computer and Systems Engineering Department Rensselaer Polytechnic Institute Troy NY 12180 Photonics Program Team Samsung Advanced Institute of Technology Suwon 440-600 Korea Republic of

ISBN: (纸本)1424400848

With the rapid development of high-power white light-emitting diodes (LEDs), advances in packaging are required to further improve the device performance. In this work, an optimized packaging configuration for high power LED lamps with enhanced phosphorescence efficiency is presented based on ray-tracing simulations and experimental results. Figure 1 shows two phosphor arrangements, namely a "proximate phosphor" and a "remote phosphor" arrangement. The surface of the reflector cup is assumed to be either specular or diffuse. Three different encapsulant geometries, i.e., a "flat" (no cap), "convex" (spherical cap with height h = r/2), and "hemispherical" (h = r) top surface, are used in the simulations. Figure 2 shows phosphorescence efficiency with different packaging configurations obtained by ray-tracing simulation. The packaging configuration with remote phosphor, diffuse reflector cup and hemispherical encapsulation shows a 50% enhancement of phosphorescence efficiency compared to conventional packaging configuration. This improvement is attributed to reduced absorption of the phosphorescence by the LED chip and the reduction of deterministic optical modes trapped inside the encapsulant of remote-phosphor and diffuse reflector cup configuration. The angular dependence of the reflectivity for a diffuse Ag reflector and a specular Ag reflector is measured and shown in Figure 3. The roughened Ag reflector has a more than two orders of magnitude higher diffusely reflected power compared with the specular Ag reflector, which leads to the extraction of the trapped optical modes occurring in packaging structures with specular reflector cups. Dichromatic LED lamps comprising an ultraviolet GaN LED (λ = 400 nm) with a blue phosphor and a blue GaInN LED (λ = 470 nm) with a yellow phosphor are fabricated with different phosphor arrangements and reflector cups. The emission spectra of the reference primary LED emitters and of the dichromatic lamps operating at 20 mA are mea

关键词： Chip scale packages

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Significance tests for MEG response detection

Significance tests for MEG response detection

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2nd International IEEE EMBS Conference on Neural engineering, 2005

作者： Ahmar, Nayef E. Wang, Yadong Simon, Jonathan Z. Department of Electrical and Computer Engineering University of Maryland College Park United States Cognitive Neuroscience of Language Laboratory University of Maryland College Park United States Department of Biology University of Maryland College Park United States Bioengineering Program University of Maryland College Park United States

Magnetoencephalography (MEG) is a non-invasive neurophysiological technique with high temporal resolution. Nevertheless, low signal to noise ratio may hamper its fullest capability. Many confidence tests already exist to detect strong responses for signals corrupted by noise, and we have explored their use with experimentally obtained MEG signals. We find that the tests demonstrating the most power are the F-test and Rayleigh's phase coherence test. Due to the strongly non-Gaussian nature of the MEG noise, from both neural and external perspective, a signal which is purely noise often fails the marginal tests by exceeding the number of false positive allowed. A variation of the tests is suggested that ensures the average false positive for a large number of responses, excited at frequencies different than the frequency of interest, is below any desired threshold. This is implemented for the F-test, Rayleigh's phase coherence test, and the union of the two. © 2005 IEEE.

关键词： Magnetoencephalography

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GPS time tag using software GPS receiver approach

GPS time tag using software GPS receiver approach

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18th International Technical Meeting of the Satellite Division of The Institute of Navigation, ION GNSS 2005

作者： Liou, L.L. Lin, D.M. Tsui, J.B. Schamus, J. Morton, J.T. Sensor Directorate Air Force Research Laboratory Wright-Patterson AFB OH Miami University Oxford OH Sensors Directory Air Force Research Laboratory Dayton OH Air Force Research Laboratory Wright Patterson AFB OH Department of Electrical and Computer Engineering Program Miami

In addition to global positioning applications, GPS has been widely used for time and frequency transfer. A GPS software receiver developed at the Air Force Research Laboratory at the Wright Patterson Air Force Base only has positioning capability, although information needed for the timing and frequency applications are already embedded in the software routines for position applications. This paper presents approaches and methods developed to extract the embedded information so that time and frequency can be accessed explicitly. Specifically, we implement GPS time tag at each output data point generated by the software tracking routine. One possible application of this work is to synchronize different GPS receivers using a common GPS reference time. The paper will discuss the relationship among several important timing quantities including the receiver bias time, GPS signal propagation time from a satellite to a from a receiver antenna to the A/D converter of the receiver front end. An analysis of the positioning solution error due to the A/D sampling frequency deviation from its nominal value is also presented, followed by the description of a software approach to calibrate the sampling frequency deviation. Two different GPS receiver front ends are used in this study to experimentally demonstrate the feasibility and validity of the time and frequency transfer functions. The nominal sampling frequencies for the two receiver front ends are 5 MHz and 5.456 MHz respectively. Using the software approach described in this paper, the sampling frequencies are calibrated to have deviations of-12 and -353 Hz, respectively, from their nominal values. For both receivers, the self-consistency tests of a single receiver using different satellites as the reference satellite were performed to evaluate the time tags precision. The self-consistent tests show that there is less than one nanosecond of time difference between the corresponding GPS time tags obtained for different refe

关键词： Signal receivers

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MEG responses to speech and stimuli with speechlike modulations

MEG responses to speech and stimuli with speechlike modulati...

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2nd International IEEE EMBS Conference on Neural engineering, 2005

作者： Xiang, Juanjuan Wang, Yadong Simon, Jonathan Z. Electrical and Computer Engineering Department University of Maryland College Park United States Cognitive Neuroscience of Language Laboratory University of Maryland College Park United States Biology Department University of Maryland College Park United States Bioengineering Program University of Maryland College Park United States

Acoustic signals can be decomposed into the product of an envelope and its fine structure. The envelope features are critical to speech recognition. Results from human behavioral and psychophysical experiments indicate that magnetoencephalography (MEG) responses can significantly phase-lock to the temporal envelope of an auditory stimulus, and speech comprehension is correlated with this phase locking. The goal of this study is to explore the properties of neural response to the speech and stimuli with complex temporal envelopes. Five auditory stimuli with the same envelope, generated from natural speech, and the same stimuli but with the envelope artificially sped up were presented to two subjects. Auditory evoked responses were recorded with a whole-head 160-channel MEG system. Independent Component Analysis (ICA), Principle Component Analysis (PCA) and equivalent current dipole fitting were performed to separate and identify the neural sources (and artifacts). The result shows that the location, orientation, and strength of the neural sources are robust across all stimuli, with correlation between auditory responses and the temporal envelope of the stimuli. These results provide support for the premise that neurons in the auditory cortex are particularly sensitive to the envelope and can phase-lock to stimuli with complex temporal and spectrotemporal envelopes. © 2005 IEEE.

关键词： Magnetoencephalography

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Modeling of spatially periodic dielectric sensors in the presence of a top ground plane bounding the test dielectric

Modeling of spatially periodic dielectric sensors in the pre...

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作者： Sheiretov, Y. Zahn, M. JENTEK Sensors Inc. 110-1 Clematis Ave. Waltham MA 02451-7013 United States Massachusetts Institute of Technology 77 Massachusetts Avenue Cambridge MA 02139 United States Eta Kappa Nu Honor Society Department of Electrical Engineering MIT MIT Course VI-A Electrical Engineering Computer Science Internship Program Liquid Dielectrics Committee International Advisory Committee International Conference on Dielectric Liquids

Semi-analytical models are used to simulate the response of periodic-field electro quasistatic dielectrometry sensors. Due to the periodic structure of the sensors it is possible to use Fourier series methods in combination with collocation point numerical techniques to generate accurate sensor simulations much more efficiently than with the more general finite-element methods. Previously, collocation-point models used to compute the response of periodic field dielectric sensors, also known as Interdigitated Electrode Dielectrometers (IDED), have ignored the contribution of the constant (zero-order) term in the Fourier series expansion of the physical quantities. This is justifiable if the top dielectric material layer under test is infinitely thick, with any top ground plane bounding the dielectric removed too far from the sensor to influence its response. This is the assumption generally made until now in the application of these models. In practice, however, it is impossible to eliminate the cumulative effect of objects at ground potential in the vicinity of the sensor, which in general manifests itself as a ground plane electrode positioned at some effective distance within the top dielectric layer (usually air). In order to eliminate this source of uncertainty in the measurements, we suggest that a grounded electrode be explicitly placed at the top of the dielectric layer in the experimental setup, and its presence be accounted for in the models. Furthermore, in many cases, such as measurements on ceramic thermal barrier coatings, a metal layer is already present behind the material under test. In this paper we present how the models must be modified to account for this ground plane, and what effect it has on the dependence of the sensor response on the material properties. For example, the sensor transcapacitance may no longer be a monotonically increasing function of the material's permittivity, leading to nonuniqueness in permittivity measurements, as some f

关键词： Dielectric devices

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Online traffic light control through gradient estimation using stochastic fluid models

Online traffic light control through gradient estimation usi...

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作者： Panayiotou, Christos G. Howell, William C. Fu, Michael Department of Electrical and Computer Engineering University of Cyprus Nicosia Cyprus Applied Mathematics Scientific Computation Program Department of Mathematics University of Maryland College Park MD 20742 United States Smith School of Business and Institute for Systems Research University of Maryland College Park MD 20742 United States

ISBN: (纸本)008045108X

in this paper, we consider the problem of dynamically regulating the timing of traffic light controllers in busy cities. We use a Stochastic Fluid Model (SFM) to model the dynamics of the queues formed at an intersection. Based on this model, we derive gradients of the queue lengths with respect to the green/red light lengths within a signal cycle. We report preliminary numerical results comparing the performance of the estimates with finite-difference and smoothed perturbation analysis estimates. Then all estimators are used to optimize the traffic system via Stochastic Approximation. Copyright © 2005 IFAC.

关键词： Stochastic systems

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Transistor characteristics of thermal chemical vapor deposition carbon nanotubes field emission triode

Journal of Vacuum Science & Technology B: Microelectronics a...

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Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena 2005年第2期23卷 868-873页

作者： Y. M. Wong W. P. Kang J. L. Davidson W. Hofmeister S. Wei J. H. Huang Department of Electrical Engineering and Computer Science Vanderbilt University Nashville Tennessee 37235 Interdisciplinary Graduate Program in Material Science Vanderbilt University Nashville Tennessee 37235 Department of Materials Science and Engineering National Tsing Hua University Hsinchu 300 Taiwan Republic of China

A study of thermal chemical vapor deposition (CVD) grown carbon nanotubes (CNTs) field emitters in a triode amplifier configuration is reported. The CNT transistor characteristics were examined by integrating gate and anode with CNT cathode in two structural forms, utilizing a TEM grid (transmission electron microscope specimen holder) as the gate electrode and a micropatterned CNT with self-aligned gate. The TEM-grid CNT triode displayed clearly gate-controlled current modulation behavior with distinct cutoff, linear, and saturation regions, and a reasonable gate turn-on field of ∼5.4V∕μm despite a large cathode-gate spacing of ∼120μm . The field emission result established the basic transistor characteristics of CNTs in a triode configuration. A CNT triode construct with a self-aligned gated fabrication technique was also developed to realize a monolithic triode structure with shorter gate-cathode spacing, lowering gate voltage, and enhancing emission current. The triode exhibited a significantly lower gate turn-on voltage of ∼40V , and gate-controlled modulation of the emission current. An anode current density of ∼30mA∕cm2 was achieved at a gate voltage of ∼80V and an anode voltage of ∼200V . The dc characteristics for both of the CNT triodes were investigated, including Ia versus Va for different Vg . Moreover, dc parameters such as transconductance, amplification factors, and anode resistance of the triode amplifier were determined. The CNT triodes exhibited useful amplification factor and high output impedance.

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Wireless hearing aid system simulations using advanced design system™: A behavioral modeling approach

Wireless hearing aid system simulations using advanced desig...

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2005 27th Annual International Conference of the engineering in Medicine and Biology Society, IEEE-EMBS 2005

作者： Rana, Ram Singh Tang, Bin Zhang, Liang Krishna, Garg Hari Wang, Yun Institute of Microelectronics Singapore Science Park II 11 Science Park Road Singapore 117685 Singapore Graduate Program in Bioengineering National University of Singapore Singapore 117597 Singapore Department of Electrical and Computer Engineering National University of Singapore Singapore 119260 Singapore Department of Otolaryngology Faculty of Medicine National University of Singapore Singapore 119074 Singapore

ISBN: (纸本)0780387406

The stringent requirements on size and power consumption constrain the conventional hearing aid devices from providing the patients an economic and user friendly solution, specifically for better noise cancellation. With the advancements in technologies such as integrated circuits design, wireless communications and digital signal processing techniques, the wireless hearing aids having multi-microphones, analog, digital and mixed signals and radio frequency signals processing circuits, DSP and programmable units seem to be promising to provide enhanced performance. The focus of this paper is about the system simulation of a typical wireless hearing aid using Agilent Advanced Design System™. The behavioral modeling features are exploited to enable the whole system simulations including electro-acoustic transducers. A few system level simulation results are included. © 2005 IEEE.

关键词： Hearing aids

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